1. Field of the Invention
The present invention relates to an image forming apparatus.
2. Description of the Related Art
Recently, there is known an image forming apparatus in which a transfer bias for transferring a toner image on an image bearer to a recording sheet is switched between a DC transfer bias including only a DC voltage and a superimposed transfer bias including a superimposed voltage of AC and DC voltages.
For example, an image forming apparatus described in Japanese Unexamined Patent Application Publication No. 2014-232127 uses the superimposed transfer bias for transferring a sufficient amount of toner to concave portions on a sheet surface, when a toner image is to be transferred to a recording sheet rich in surface asperities such as Japanese paper in a transfer nip. By reciprocating the toner by the AC component of the superimposed transfer bias, a sufficient amount of toner can be transferred to the concave portions on the recording sheet. Meanwhile, when a toner image is to be transferred to a recording sheet having excellent surface smoothness such as plain paper, because a sufficient amount of toner can be transferred to the sheet surface without reciprocating the toner, the DC transfer bias is used.
However, in such a configuration, there is a problem that insufficient image density is likely to occur at an end portion of a sheet, in any of a recording sheet rich in surface asperities and a recording sheet having excellent surface smoothness.